Thermal characteristics at interface of Bi2Te 3/Sb2Te3 superlattices

To consider the thermal characteristics of a Bi2Te 3/Sb2Te3 superlattice, we analyzed the phase lag of ac temperature waves between front and rear surfaces when an ac heat flux was applied to the front surface. In this analysis, we examined two typical models. In one model, a sharp interface exists between the adjacent layers in the superlattice where two crystals abruptly face each other at the interface. In the other model, an interfacial region composed of a disordered structure exists between the adjacent layers where the lattice constant and/or the chemical composition of the two adjacent layers are relaxed in the interfacial region. We found that both models could explain the experimental results almost equivalently. So far it has been known that in many cases the interface between adjacent crystals has a relaxed region where a disordered structure exist, and its width is comparable to phonon mean free path at room temperature. To understand the characteristics of the thermophysical properties at an interface, it is important to know the structure of the interfacial region.